1. Field of the Invention
This invention relates to a boot used for sealing, for example, the operating part of a universal joint, and a connecting method, welding agent and heating body therefor.
2. Description of the Prior Art
In this type of boots, mounting parts present on both axial ends thereof are mounted, for example, on the outer race and joint shaft of a universal joint, whereby the bellows-formed flexible part of the boot is flexibly expanded and contracted to prevent the intrusion of an external foreign matter to the operating part of the universal joint and, further, to seal the oil and fat such as grease filled in the operating part.
In a conventional split type boot, which is one type of the above-described boots, a rubber-made boot is divided in one circumferential part. A plurality of fasteners consisting of male connecting member and female connecting member arranged at prescribed intervals is integrally provided on each of the circumferentially opposed split end parts. In mounting, the boot is put over a universal joint from the side by opening the split part. The fasteners are coupled and also adhered together by an adhesive, whereby the split end parts are mutually connected in the closely fitted state.
The boot is rotated in the state where the shaft centers of the outer race and joint shaft having both the axial end mounting parts fixed thereto are mutually inclined. Accordingly, the bellows part repeats bending and stretching motions every half period of the rotation. In the split boot, the repeated bending and stretching of the mutually adhered divided end parts induce the danger of the hardened adhesive layer causing a deterioration such as crack by fatigue, resulting in the early leakage of the grease within the universal joint. Further, it is necessary to provide the male connecting member and female connecting member of the fasteners in the divided end parts with high precision. It is also necessary to ensure the sealing property of the fasteners by applying a coating agent or the like because of its low sealing property. Further, their scanty following property to the bending and stretching deformation of the boot induces the danger of its breakage within a short period.
This invention has an object to improve the sealing performance and fatigue strength in the opposed split end parts of a split type boot and also improve the working property in mounting.
A split type boot according to one embodiment of this invention is a cylindrical boot divided in one circumferential part, in which a protruding part and recessed part extending along the sectional form of the boot are formed on the circumferentially opposed split end parts to be integrally connected in mounting, respectively. The protruding part on one split end part and the recessed part on the other split end part have the forms to be hooked (engagingly locked) to each other in one thickness directional side. An overlapping protruding part is protruded longer than the protruding part on the non-hook (lock) side in the recessed part, and connected extending over the protruding part and the one split end part.
Both the axial end mounting parts of the boot are preferably formed of a rubber-like elastic material more elastic than the boot. The boot is mounted on the outside surface of a counter material through a packing divided in one circumferential part.
A split type boot according to another embodiment of this invention is provided with an open part formed by dividing one circumferential part thereof, and mounted by connecting the open part after covering a mounting member such as universal joint. The open part is connected by heating and welding it by a heating body having self-heating property.
In a connecting method for a split boot according to a further embodiment of this invention, the boot has an open part formed by dividing one circumferential part thereof, and the open part is connected after covering a mounting member such as universal joint. A heating body having self-heating property is brought into contact with or approached to the open part to heat and weld the open part by the heating body.
A welding agent according to an additional embodiment of this invention is a welding agent used in the connection of the open part formed by dividing one circumferential part after covering a mounting member such as universal joint, and it is applied to the opposed surfaces of the open part to weld the opposed surfaces together.
A preferable welding agent according to this invention consists of a solvent for dissolving a thermoplastic elastomer. The welding agent is formed of a simple body or mixture of solvents, for example, dimethylformamide, tetrahydrofuran, toluene, ethyl acetate, methyl ethyl ketone, acetone, cyclohexanone, and dichloromethane.
A heating body according to another embodiment of this invention is a heating body used in the connection of the open part formed by dividing one circumferential part, which has self-heating property, and is fixed to the boot to heat and weld the open part in contact with or adjacent to the open part.
A preferred heating body according to this invention is formed of an amorphous bag and a heating component put therein so as to be deformable following the bellows form of the boot.
Further preferably, an irregular form laid along the irregularities of the bellows is preliminarily imparted to the outer surface of the heating body so as to closely fit to the open part along the bellows form of the boot.
According to a preferred split type boot of this invention, satisfactory sealing property is ensured for the mutually connected split parts of the boot in the state mounted on a mounting member such as universal joint, because the protruding part and recessed part are continuously extended on the split end parts of the boot, and the fitting surfaces thereof are integrated together by welding, fusion or adhesion. Further, because a large connecting area can be ensured by forming, on the non-hook side of the recessed groove, the overlapping protruding part to be connected extending over the protruding part and the one split end part continued thereto.
Further, the protruding part is set to the form to be hooked (engagingly locked) with the recessed part in one thickness directional side, whereby the split end parts can be thinned, compared with the case of forming the hook part (locking part) on both thickness directional sides. Therefore, the insert resistance in the temporary connection of the split end parts can be minimized by insert-engaging the protruding part with the recessed part, and the superposing protruding portion also guides the insertion, so that the temporary connecting work can be easily performed. Further, since the increase in stress by the repeated bending and stretching deformation can be suppressed, the fatigue durability can be improved.
When both the axial end mounting parts of the boot are mounted on the outside surface of a counter member such as universal joint through packings formed of a rubber-like elastic material more elastic than the boot, the sealing property in the mounting parts can be improved.
In a preferable boot according to this invention, the boot is manufactured without mounting fasteners on the opposed surfaces of the open part, and when the boot is mounted on the circumference of a mounting member such as universal joint, a welding agent is applied to the opposed surfaces of the open part to mutually weld the opposed surfaces together. In such a welding of the open part, the open part is heated and welded by a heating body having self-heating property, whereby the welding reaction or connecting reaction is promoted. The open part connected by welding is excellent in sealing property since the opposed surfaces are integrated together. Further, it is deformable following the deformation of the bellows part. To have self-heating property means exhibiting the heating effect for itself in use and requiring no supply of external energy as electric power. To ensure the connecting property by welding, a thermoplastic elastomer is preferably used as the material of the split type boot. To sufficiently exhibit the performance as the boot, a polyurethane thermoplastic elastomer or polyester thermoplastic elastomer highly strong and excellent in durability are preferably used.
In a preferred connecting method for a boot according to this invention, the boot is manufactured without mounting fasteners on the opposed surfaces of the open part, and when this boot is mounted on the circumference of a mounting member such as universal joint, a welding agent is applied to the opposed surfaces of the open part to weld the opposed surfaces together. In such a welding of the open part, the heating body having self-heating property is brought into contact or approached, and the open part is heated and welded by this heating body, whereby the welding reaction or connecting reaction is promoted. The open part connected by welding is excellent in sealing property since the opposed surfaces are integrated together. Further, it is deformable following the deformation of the bellows part. As the heating body having self-heating performance, a one mainly composed of iron powder, water, activated charcoal and salt or of a metal oxide and water, and generating heat mainly by oxidization reaction or reduction reaction is preferably used. Further, any other materials having self-heating performance can be used.
The heating body used for the connection of the open part is preferably formed of a permeable bag of paper, nonwoven fabric or cloth and a heating component mainly composed of iron powder, water, activated charcoal and salt or of a metal oxide and water and put therein. When a shielding film-like outer packaging enclosing this heating body is opened, the moisture in the air touches the iron to cause the oxidation reaction of the iron, or the metal oxide is reacted with water to cause the reduction reaction. High heat is generated according to this, so that the open part can be heated and welded by this high heat. In order to satisfactorily transfer the heat of the heating body to the open part in spite of the presence of the irregularities (mountain/valley) by the bellows part on the outer surface of the boot, the heating body is preferably closely fitted to the overall outer surface of the open part by putting the heating component in an amorphous bag or preliminarily imparting the irregular form laid along the irregularities of the bellows to the outer surface of the heating body. According to this, the heating body is closely fitted or approached to not only the protruding part (mountain part) of the bellows but also the recessed part (valley part) thereof to raise the temperature of the recessed part substantially equally to the temperature of the protruding part. Thus, the temperature of the whole open part can be uniformly raised, and the welding time can be thus consequently shortened.
To heat the open part, a dryer for blowing hot air, for example, can be used. In this case, however, a person must perform the work with the dryer in its hand in constant attendance until the welded part is sufficiently dried. A constraining means must be separately provided so that the open part is not opened in the middle of welding to keep the open part in the closed state. Further, the blowing of hot air may possibly cause a large dispersion of temperature between the part exposed to the hot air and the part not exposed to the hot air.
Contrary to this, when the heating body is fixed to the outer surface of the open part of the boot to perform the welding, the work can be progressed without attendance of a person in drying. The open part can be kept in the closed state until the welded part is dried without separately providing the different constraining means. Further, the heating temperature can be easily made constant. An external heat energy source such as power source apparatus or heating light is dispensed with.
To fix the heating body to the outer surface of the open part of the boot, a mounting means such as adhesive sheet, adhesive tape, tying cord, stretchable cloth or hook-and-loop fastener is preferably used.